Organic Light Emitting Diode (OLED), as a current-type light emitting element, has become a mainstream display element in current display devices because of its light weight, fast response and high contrast. According to the driving modes, i.e., PMOLED (Passive Matrix Driving OLED) and AMOLED (Active Matrix Driving OLED), AMOLED has the advantages of shorter driving time and lower power consumption.
Prior to the normal operation stage of an OLED pixel compensation circuit, the pixel compensation circuit is first powered on and performed the panel short circuit detection by an SSD (Short Circuit Detection) circuit. FIG. 1 shows a conventional OLED pixel compensation circuit in the prior art. The pixel compensation circuit comprises a driving transistor (for example, driving thin-film transistor, DTFT) the source of which is coupled to the EL high level ELVDD of the pixel compensation circuit in a Direct Current-Direct Current (DC-DC) control circuit, the gate of which is coupled to a reset voltage input Vinit, a reference voltage input Vref and a data signal input Vdata, the drain of which is connected to the anode of an OLED display element, the voltage of the cathode of the OLED display element being the EL low level ELVSS of the pixel compensation circuit. The SSD circuit detects the EL low level ELVSS of the pixel compensation circuit. When there is a short circuit on an OLED display device, for example, when a component is damaged or breaked down, a leakage current is generated in the display element, and the leakage current can be detected by the SSD circuit so that the high level ELVDD of the DC-DC output is turned off in time. FIG. 2 shows a typical DC-DC driving timing for the OLED pixel compensation circuit in the prior art. In the power-on process of the pixel compensation circuit, at first the reference voltage input Vref rises to the rated reference voltage, the reset voltage input Vinit drops to the rated reset voltage, then the EL high level ELVDD is input, and the gate-source voltage of the driving thin-film transistor DTFT turns on the DTFT, and the drain outputs the current for driving the display element.
In the conventional driving timing for the pixel compensation circuit of the display device, the EL low level ELVSS is output 10 ms after outputting the EL high level ELVDD, and the SSD circuit begins the detection at the time when outputting the ELVSS, i.e., 10 ms after outputting the ELVDD. However, during this 10 ms period, an abnormal display may occur at the first frame of the outputting of the EL high level ELVDD, which causes a large current, resulting in the generation of the leakage current. The large current lifts the EL low level ELVSS, i.e. the test node voltage of the SSD circuit, resulting in turning on the ESD diode at the EL low level ELVSS end of the DC-DC circuit. For example, the SSD circuit detects an EL low level ELVSS voltage of 700 mV, which is greater than the threshold voltage of 200 mV, then the SSD circuit will erroneously determine the lifting of the EL high level ELVDD as a panel short circuit fault and cut off the output of the DC-DC circuit, and the display device cannot be lit up due to the lack of the EL voltage, i.e., the EL high level ELVDD and the EL low level ELVSS. The above defects of the pixel compensation circuit of the conventional OLED driving circuit will cause the problem that the display panel has a splash screen phenomenon during the power-up and the panel cannot be lit up due to a DC-DC failure.